Searching for dolerites around Isfjorden

Early Cretaceous dolerites in Spitsbergen: a virtual field trip to the most accessible HALIP exposures

By Kim Senger, The University Centre in Svalbard, kim.senger@unis.no

 

Early Cretaceous magmatism associated with the early phase of the High Arctic Large Igneous Province (HALIP) led to the emplacement of significant magmatic volumes across the circum-Arctic. In Svalbard, HALIP magmatism is manifested by predominantly basaltic intrusions and lava flows collectively classified as the Diabasodden Suite, named after the Diabasodden type locality in central Spitsbergen. Here the dolerites primarily occur as sills intruded in Permian-Jurassic siliciclastic host rocks, with dykes present locally. As in other volcanic basins worldwide, the Svalbard intrusions have had an impact on the various petroleum system elements and compartmentalize a siliciclastic reservoir-cap rock system locally targeted for CO2 storage.

During this virtual excursion we will circum-navigate Isfjorden and visit a number of localities where the Early Cretaceous dolerites are exposed. The figure below provides an overview of the main theme of each of the subsequent stops. Even though we are running this excursion virtually, we are exactly following the route taken by four geologists in August 2019 onboard the research vessel “Clione”, and it is thus only natural that we start the excursion by boarding the sailboat in Longyearbyen harbour and start steaming towards the north-west.

Schematic overview of the storyline for the virtual field trip through the Diabasodden Suite of central Spitsbergen. The storyline provides key themes for each stop on the virtual excursion.

 

Background reading:

The following articles provide overviews of the Svalbard dolerites, and are useful reading prior to embarking on the virtual field trip!

Maher, H. D., Jr, 2001, Manifestations of the Cretaceous High Arctic Large Igneous Province in Svalbard: The Journal of Geology, 109, no. 1, 91-104. http://dx.doi.org/10.1086/317960.

Nejbert, K., K. P. Krajewski, E. Dubińska, and Z. Pécskay, 2011, Dolerites of Svalbard, north-west Barents Sea Shelf: age, tectonic setting and significance for geotectonic interpretation of the High-Arctic Large Igneous Province: Polar Research, 30, no. 7306, 1–24. http://dx.doi.org/10.3402/polar.v30i0.7306.

Senger, K., J. Tveranger, K. Ogata, A. Braathen, and S. Planke, 2014, Late Mesozoic magmatism in Svalbard: A review: Earth-Science Reviews, 139, 123-144. http://dx.doi.org/http://dx.doi.org/10.1016/j.earscirev.2014.09.002.

Dallmann, W., 2015, Geoscience Atlas of Svalbard: Norsk Polarinstitutt Rapportserie, 148, 292. Available at https://brage.npolar.no/npolar-xmlui/handle/11250/2580810

 

 

Stop 1: Geological overview at Festningen

Our first stop at Festningen is a couple of sailing hours due west of Longyearbyen. En route there we pass several Russian abandoned coal-mining settlements including Grumant and Colesbay, as well as the operational coal mining settlement of Barentsburg. The Festningen profile provides a unique opportunity to examine the Paleozoic-Mesozoic succession of Spitsbergen while strolling along a coastal section. Festningen is located in western Spitsbergen and thus heavily affected by the West Spitsbergen Fold and Thrust Belt. The strata are thus severely inclined, as illustrated by drone footage of the Festningen sandstone near the easternmost, youngest, part of the Festningen profile.

The Festningen profile in April 2019, looking westwards. The dominant wall comprises the sandstones of the Cretaceous Helvetiafjellet Formation. Note snowmobiles for scale. 

 

The Festningen Section stretches from the Permian Kapp Starostin Formation to the Grønnfjorden Bed at the base of the Paleogene Firkanten Formation. The geological map and stratigraphic profile below both illustrate the

Geological map of the Festningen area. Mapping by Norwegian Polar Institute, figure from Mørk and Worsley (2006).

 

Schematic interpretative section through the sediments from the Late Permian to the base Cenozoic. Thickness values are approximate as strong compression may have taken place in the shaly units. Figure and caption from Mørk and Worsley (2006).

 

The figure below illustrates a magnetic profile (green line) taken across the Festiningen profile during the Svalex expeditions. Note the strong anomaly in the lower part of the Vikinghøgda Formation, associated with an igneous sill.

Magnetic profile (green line) across the Festningen profile, illustrating a strong magnetic anomaly at the base of the Vikinghøgda Formation, co-inciding with an igneous sill. Figure from SvalSIM, data compiled and collected by Svalex expeditions.

 

Similar-sized sills are also penetrated by exploration boreholes in the central part of the Central Tertiary Basin. The Colesbukta borehole, located 26 km east of Festningen, penetrates a 42 m thick sill in a similar stratigraphic position. The Ishøgda borehole, on the shore of Van Mijenfjorden, offers a ca. 55 m thick sill within the Botneheia Formation. The exploration boreholes nicely illustrate the petrophysical signature of the intrusions, being characterized by low gamma ray and high sonic and resistivity. Finally, the regional Festningen to well correlation provides an overview of the wide range of potential host rocks for the Diabasodden Suite intrusives, notably Permian carbonates and Triassic siliciclastic deposits.

Correlation panel from Festningen to the two deepest petroleum exploration boreholes drilled in Svalbard, at Colesbukta and Ishøgda. 

 

Additional reading relevant for the stop:

Mørk, A., and D. Worsley, 2006, The Festningen section: Norsk Geologisk Forening (NGF) Abstracts and Proceedings, 3, 31-35.

Senger, K., P. Brugmans, S.-A. Grundvåg, M. Jochmann, A. Nøttvedt, S. Olaussen, A. Skotte, and A. Smyrak-Sikora, 2019, Petroleum, coal and research drilling onshore Svalbard: a historical perspective: Norwegian Journal of Geology, 99, no. 3. http://dx.doi.org/dx.doi.org/10.17850/njg99-3-1.

Worsley, D., 2008, The post-Caledonian development of Svalbard and the western Barents Sea: Polar Research, 27, 298-317. http://dx.doi.org/10.1111/j.1751-8369.2008.00085.x.

 

Stop 2: Mediumfjellet and the West Spitsbergen Fold and Thrust Belt

From Festningen we head north across Isfjorden, sheltering in Yoldiabukta beneath Mediumfjellet. Mediumfjellet is a characteristic mountainside visible from Longyearbyen on clear days – it is bounded by the presently surging Wahlenbergbreen on the southern side, and by Sveabreen to the north. Geologically, the mountain is heavily affected by Cenozoic transpression during the formation of the West Spitsbergen Fold and Thrust Belt (WSFTB), as evidenced by the overview imagery in the video below.

The lighter steep units belong to the Permian spiculite-bearing Kapp Starostin Formation, while the darker units are primarily part of the overlying Triassic siliciclastic deposits.

 

Additional reading relevant for the stop:

Bergh, S. G., and A. Andresen, 1990, Structural development of the Tertiary fold-and-thrust belt in east Oscar II Land, Spitsbergen: Polar Research, 8, no. 2, 217-236. http://dx.doi.org/10.1111/j.1751-8369.1990.tb00385.x.

Johansen, S. E., S. Kibsgaard, A. Andresen, T. Henningsen, and J. R. Granli, 1994, Seismic modeling of a strongly emergent thrust front, West Spitsbergen fold belt, Svalbard: AAPG bulletin, 78, no. 7, 1018-1027.

Braathen, A., and S. G. Bergh, 1995, Kinematics of Tertiary deformation in the basement-involved fold-thrust complex, western Nordenskiöld Land, Svalbard: tectonic implications based on fault-slip data analysis: Tectonophysics, 249, no. 1, 1-29.

Larsen, T., 2010, Fractured carbonates in the Mediumfjellet thrust-stack in the Tertiary fold-and-thrust belt of Spitsbergen, University of Tromsø.

Strand, S. A. H., 2015, Layer parallel shortening and cataclastic flow by fractures in the Permian Kapp Starostin Formation, Mediumfjellet, Spitsbergen, The University of Bergen.

 

Stop 3: Igneous intrusions in carbonate-dominated successions, Ekmanfjorden and Dicksonfjorden

From Yolidabukta we head north, and spend the night in the shelter of the Coraholmen island that protects us from the northerly waves and wind. In the morning we leave Clione behind and start the longish climb up to Kolloseum, with ambitions to sample the dolerites mapped on its top. After 2.5 hours of hiking through carbonate-dominated successions we reach the breath-taking ridge only to realise that most of the southern part is dominated by carbonates, and not dolerites. The 360 degree view is nonetheless amazing, especially from the drone’s perspective some 10s of meters above the ground.

 

The drone also allows us to locate the dolerite several kilometres further north, as well as on numerous localities on the eastern shore of Ekmanfjorden. We leave the area only sampling a loose dolerite block and plan to return to the area for detailed mapping in the future.

Aerial overview looking northwards along the ridge of Kolloseum. Note the dolerite on the highest point of the ridge. 

 

As we leave Ekmanfjorden we make a brief stop on the northern tip of Blomesletta to sample the well exposed dolerite and acquire an overview 360 panorama across Ekmanfjorden.

 

 

Additional reading relevant for the stop:

Bates, D., and W. Schwarzacher, 1958, The geology of the land between Ekmanfjorden and Dicksonfjorden in central Vestspitsbergen: Geological Magazine, 95, no. 3, 219-233.

Lauritzen, Ø., 1981, Investigations of Carboniferous and Permian sediments in Svalbard.

 

 

Stop 4: Influence of igneous intrusions on fluid flow: pockmarks and their distribution in Nordfjorden

As we cruise southwards along the shores of southern Dickson Land it is worthwhile to consider what is beneath the calm sea. Nordfjorden is a tributary of the major Isfjorden fjord, and is one of few places where active gas seepage has been identified using acoustic flares in the water column. In addition, there are numerous pockmarks testifying past fluid migration. Many of these are aligned with positive relief features on the seabed, which are often associated either with Cenozoic thrust faults or Early Cretaceous igneous intrusions.

Multibeam high-resolution bathymetric data in Nordfjorden, illustrating the presence of pockmarks, seafloor ridges and gas-charged sediments. Figure from Roy et al. (2019).

 

The figure below illustrates one of these seafloor ridges in detail. Partly based on the 2D seismic data acquired as part of the Svalex excursions the ridge is interpreted to be related to an igneous sill offset by a thrust fault. In some areas, sills reach the seafloor and pockmarks occur preferentially along its lower contact. This suggests that sill contacts may act as preferential fluid migration pathways.

Bathymetric data, interpretation of pockmarks associated with W-E striking ridge R1 and seismic line across the ridge. Figure from Roy et al. (2019). 

 

The figure below summarizes the main findings of the integrated sub-surface study of Nordfjorden, linking deep and shallow seismic with the seafloor and water column evidence for past and ongoing fluid seepage.

Conceptual model of seabed fluid flow and seepage in Nordfjorden: Gas accumulation in marine sediments and seepage at seafloor are controlled by subsurface
tectonic features and igneous sills. Occurrence of pockmarks in the southern part of the study area is primarily influenced by sub-cropping thrust faults and
that in the northern part by igneous sills. Figure and caption from Roy et al. (2019). 

 

As we leave Nordfjorden we pass by Tschermakfjellet, with its characteristic igneous intrusion well appreciated both from boat and drone.

 

Additional reading relevant for the stop:

Roy, S., Senger, K., Hovland, M., Römer, M. & Braathen, A. 2019: Geological controls on shallow gas distribution and seafloor seepage in Arctic fjord of Spitsbergen, Norway. Marine and Petroleum Geology.

Roy, S., K. Senger, R. Noormets, A. Braathen, and S. Olaussen, 2014, Fluid migration pathways to seafloor fluid seepage in inner Isfjorden and Adventfjorden, Svalbard: Norwegian Journal of Geology, 94, 99-119.

Senger, K., J. Millett, S. Planke, K. Ogata, C. Eide, M. Festøy, O. Galland, and D. Jerram, 2017, Effects of igneous intrusions on the petroleum system: a review: First Break, 35, no. June, 10. http://dx.doi.org/10.3997/1365-2397.2017011.

Liira, M., R. Noormets, H. Sepp, O. Kekišev, M. Maddison, and S. Olaussen, 2019, Sediment geochemical study of hydrocarbon seeps in Isfjorden and Mohnbukta: a comparison between western and eastern Spitsbergen, Svalbard: arktos, 1-14.

 

 

Stop 5: A possible hydrothermal vent complex in Isfjorden

Hydrothermal vent complexes have received significant attention in recent years, particularly as they provide an effective mechanism for transporting greenhouse gases generated within contact aureoles of sills empalced at depth to the paleosurface. Hydrothermal vent complexes are, as illustrated below, often initiated at the tips of sills, and consist of a pipe-like structure in the lower part and a crater at the paleosurface.

Schematic diagram of a hydrothermal vent complex. Figure from Svensen et al. (2006). 

 

Just south of Kapp Thordsen, a significant, semi-circular positive relief feature is apparent on the seafloor, as shown below. Numerous pockmarks in its vicinity also testify to fluid migration.

Positive relief features in Isfjorden thought to be associated with igneous activity, including a potential hydrothermal vent complex and a fluid-channeling sill in Sassenfjorden. Figure from Senger et al. (2013).

 

Magnetic data acquired as part of seismic acquisition suggest a magnetically low feature, favouring the hydrothermal vent complex interpretation instead of a volcanic stock.

Magnetic data across the positive relief anomaly shown in the figure above. Figure modified from Senger et al. (2013). 

 

 

Additional reading relevant for the stop:

Senger, K., Roy, S., Braathen, A., Buckley, S. J., Bælum, K., Gernigon, L., Mjelde, R., Noormets, R., Ogata, K., Olaussen, S., Planke, S., Ruud, B. O. & Tveranger, J. 2013: Geometries of doleritic intrusions in central Spitsbergen, Svalbard: an integrated study of an onshore-offshore magmatic province with implications on CO2 sequestration. Norwegian Journal of Geology 93, 143-166.

Svensen, H., Jamtveit, B., Planke, S. & Chevallier, L. 2006: Structure and evolution of hydrothermal vent complexes in the Karoo Basin, South Africa. Journal of the Geological Society 163, 671-682.

Svensen, H., S. Planke, A. Malthe-Sorenssen, B. Jamtveit, R. Myklebust, T. Rasmussen Eidem, and S. S. Rey, 2004, Release of methane from a volcanic basin as a mechanism for initial Eocene global warming: Nature, 429, no. 6991, 542–545. http://dx.doi.org/10.1038/nature02566.

Polteau, S., B. W. Hendriks, S. Planke, M. Ganerød, F. Corfu, J. I. Faleide, I. Midtkandal, H. S. Svensen, and R. Myklebust, 2016, The Early Cretaceous Barents Sea Sill Complex: Distribution, 40 Ar/39 Ar geochronology, and implications for carbon gas formation: Palaeogeography, Palaeoclimatology, Palaeoecology, 441, 83-95.

 

Stop 6: Svenskehuset and southern Dickson Land

Svenskehuset (“the Swedish House”) is the site of one of the most tragic stories from Svalbard – being the site where 17 sealers perished due to lead poisoning while unwantedly overwintering there in 1872-1873 (see Aasebø & Kjær 2009 for the full sotry). The house itself is very large for Svalbard, and was initially built to try to mine phosphorite from Saurieberget above the house. The Triassic strata in the immediate vicinity of Svenskehuset and the entire southern Dickson Land is heavily intruded by sills, with dykes present locally (see next stop).

Overview footage of Svenskehuset and the surrounding dolerites of Saurieberget.

 

First-order field mapping in southern Dickson Land identified a number of sills cutting across valleys at relatively long km-scale distances. The outcrops display some transgressive segments, sill-stepping and even some dykes. Sill thickness is usually in the 10s of metres, though some thinner, m-scaled, sills are also present.

Overview of the igneous complex in southern Dickson Land, with orientations of the intrusion contacts from field measurements. Figure from Senger et al. (2013). 

 

An initial attempt to correlate the igneous complex is presented below, and suggests that many of the intrusions in southern Dickson Land occur as layer-parallel sills. In Studentdalen, stacked sills are well exposed.

Synthesis of igneous intrusion presence in southern Dickson Land. Figure from Senger et al. (2013). 

 

 

Additional reading relevant for the stop:

Aasebø, U., and K. G. Kjær, 2009, Lead poisoning as possible cause of deaths at the Swedish House at Kapp Thordsen, Spitsbergen, winter 1872-3: BMJ, 339, 1-4. http://dx.doi.org/10.1136/bmj.b5038.

Senger, K., S. Roy, A. Braathen, S. J. Buckley, K. Bælum, L. Gernigon, R. Mjelde, R. Noormets, K. Ogata, S. Olaussen, S. Planke, B. O. Ruud, and J. Tveranger, 2013, Geometries of doleritic intrusions in central Spitsbergen, Svalbard: an integrated study of an onshore-offshore magmatic province with implications on CO2 sequestration: Norwegian Journal of Geology, 93, 143-166.

 

Stop 7: Dykes in Spitsbergen, particularly beneath Rotundafjellet and on Botneheia

Dykes are less common than sills in Spitsbergen but have been mapped in both central Spitsbergen, southern Spitsbergen and on magnetic data east of Svalbard. A good example of a dyke directly feeding a sill is visible on the northern shore of Isfjorden. The dyke is approximately 6 m thick, and illustrates increased fracturing near the chilled margins.

Dolerite dyke and associated contact aureoles beneath Rotundafjellet, southern Dickson Land. Figure from Festøy (2017).

 

The regional distribution of dykes in Svalbard and the circum-Arctic is based on field mapping magnetic data. Buchan & Ernst (2018) argue that the dykes form a series of radial and circumferential dykes around the Alpha Ridge, both of which become apparent when the Eurasia Basin is closed to its pre-opening position. More complicated models involving pure shear bands with conjugate systems of the Svalbard and Franz Josef Land dyke swarms have been proposed by Minakov et al. (2018).

The proposed Circum-Arctic HALIP dyke swarm. Figure from Buchan & Ernst (2018). 

 

 

Additional reading relevant for the stop:

Festøy, M., 2017, Integrated characterization of igneous intrusions in Central Spitsbergen, University of Tromsø/UNIS.

Festøy, M. H., K. Senger, and S.-A. Grundvåg, 2018, Fracture networks in and around igneous intrusions on Svalbard: implications for fluid flow: 33rd Nordic Geological Winter Meeting.

Senger, K., S. Roy, A. Braathen, S. J. Buckley, K. Bælum, L. Gernigon, R. Mjelde, R. Noormets, K. Ogata, S. Olaussen, S. Planke, B. O. Ruud, and J. Tveranger, 2013, Geometries of doleritic intrusions in central Spitsbergen, Svalbard: an integrated study of an onshore-offshore magmatic province with implications on CO2 sequestration: Norwegian Journal of Geology, 93, 143-166.

Minakov, A., Yarushina, V., Faleide, J. I., Krupnova, N., Sakoulina, T., Dergunov, N. & Glebovsky, V. 2018: Dyke emplacement and crustal structure within a continental large igneous province, northern Barents Sea. Geological Society, London, Special Publications 460, 371-395.

Buchan, K. L. & Ernst, R. E. 2018: A giant circumferential dyke swarm associated with the High Arctic Large Igneous Province (HALIP). Gondwana Research.

Birkenmajer, K. & Morawski, T. 1960: Dolerite intrusions of Wedel-Jarlsberg Land, Vestspitsbergen. Studia Geologica Polonica IV, 103-123.

Hagevold, S., 2019, From outcrop to synthetic seismic: 2D and 3D modelling of igneous intrusions at Botneheia, central Spitsbergen, The University of Bergen.

 

Stop 8: Contact metamorphism around thick and thin intrusions

Contact metamorphic processes can have a major implication on releasing hydrocarbons and other greenhouse gases from the host rock. Even though the regions affected is relatively minor, typically up to twice the thickness of the intrusion, in volcanic basins these can release significant material to the atmosphere, particularly if hydrothermal vent complexes are present (see stop 5). In Svalbard, a thin intrusion penetrated by the DH4 research borehole has been drilled and fully cored, and subsequently analysed using Rock-Eval to constrain the total aureole thickness of the 2.28 m thick intrusion to be ca 160-195% of the thickness.

Results of the geochemical analyses of aureole samples. The geological log illustrates the visible extent of the aureole away from the 2.28 m-thick intrusion, along with the sample depths. Refer to the text for details on the parameters and interpretation. Figure and caption from Senger et al. (2014). 

 

Hubred (2006) analyses samples taken at progressively increasing distance from a thicker (ca 30 m) sill at Botneheia in central Spitsbergen. The results, and the aureole thicknesses calculated from two exploration boreholes in Svalbard (see Stop 1) suggest that there is a good correlation across intrusion scales, as illustrated below.

 

Correlation between intrusion and aureole thickness in Svalbard, using publications and well bore data.

 

 

Additional reading relevant for the stop:

Senger, K., Planke, S., Polteau, S., Ogata, K. & Svensen, H. 2014: Sill emplacement and contact metamorphism in a siliciclastic reservoir on Svalbard, Arctic Norway. Norwegian Journal of Geology 94, 155-169.

Hubred, J. H. 2006: Thermal Effects of Basaltic Sill Emplacement in Source Rocks on Maturation and Hydrocarbon Generation. Unpublished MSc, University of Oslo, 303 pp.

Brekke, T., Krajewski, K. P. & Hubred, J. H. 2014: Organic geochemistry and petrography of thermally altered sections of the Middle Triassic Botneheia Formation on south-western Edgeøya, Svalbard. Norwegian Petroleum Directorate Bulletin 11, 111-128.

Aarnes, I., H. Svensen, J. A. D. Connolly, and Y. Y. Podladchikov, 2010, How contact metamorphism can trigger global climate changes: Modeling gas generation around igneous sills in sedimentary basins: Geochimica et Cosmochimica Acta, 74, 7179–7195. http://dx.doi.org/10.1016/j.gca.2010.09.011.

 

 

Stop 9: Botneheia, Hyperittfossen and Grønsteinfjellet

The igneous intrusion complex between Vindodden and Hatten offers much more complex geometries than the units in southern Dickson Land. Both thick and thin sills are present, as well as more significant dykes. The main sill is continueously exposed across the entire area, though it transgresses stratigraphy several times. In addition, the Botneheia mountain offers the intrusion that penetrates highest in the stratigraphy in the Isfjorden area – a dyke that cuts into the Late Jurassic Agardhfjellet Formation shale-dominated units. As such, it also penetrates the reservoir-cap rock of the Longyearbyen CO2 lab project – a topic for a future virtual field trip!

Aerial image with intrusions highlighted in the Vindodden-Hatten exposures in central Spitsbergen. Figure from Senger et al. (2013). 

 

One of the most spactacular features on the transect from Vindodden to Hatten is Grønsteinfjellet, a mountainside incorporating a transgressive sill and a cross-cutting dyke. The video below shows some of the features visible from the western margin of Grønsteinfjellet, including the Diabasodden Suite type locality in the background.

 

Additional reading relevant for the stop:

Senger, K., S. Roy, A. Braathen, S. J. Buckley, K. Bælum, L. Gernigon, R. Mjelde, R. Noormets, K. Ogata, S. Olaussen, S. Planke, B. O. Ruud, and J. Tveranger, 2013, Geometries of doleritic intrusions in central Spitsbergen, Svalbard: an integrated study of an onshore-offshore magmatic province with implications on CO2 sequestration: Norwegian Journal of Geology, 93, 143-166.

Hagevold, S., 2019, From outcrop to synthetic seismic: 2D and 3D modelling of igneous intrusions at Botneheia, central Spitsbergen, The University of Bergen.

 

Goodbye, and hope you enjoyed the virtual trip around Isfjorden!

Please direct any comments regarding this virtual field trip to Kim Senger (kim.senger@unis.no).and please stay tuned to the Svalbox website for more Svalbard geological experiences.